Explosive mine



May 19, 1925. 1,538,316

J. .1. DUFFIE EXPLOSIVE MINE Filed Feb. 8, 1,?18 5 Sheets-Sheet 1 I A TTORNEIQY.

J. J. DUFFIE EXPLOSIVE MINE Filed Feb. 8, 1918 5 Sheets-Sheet 2 FIG-2 LVVENTOR.

J. J. DUFFIE EXPLOSIVE MINE Filed Feb. 8, 1918 3 Sheets-Sheet 5 FIGS.

INVENTOR. John/awe,

BY f

ATTORNEXJ.

Patented May 19, 1925.

JOHN J. DUFFIE, 0F BERKELEY,

CALIFORNIA, A$SIGNOR TO GOVERNMENT OF THE UNITED STATES.

EXPLOSIVE MINE.

Application filed February 8, 1918. Serial No. 215,970.

To all whom it may concern:

Be it known that I, JOHN J. DUFFIE, a citizen of the United States, residing at Berkeley, in the county of Alameda and State of California, have invented certain new and useful Improvements in Explosive Mines, of which the following is a specification.

My invention pertains to mines such as are used for the protection of harbors, channels, and like places, and consists essentially in providing such mines with automatic means for effecting their detonation and explosion when a vessel, either surface or submersible, approaches within a given distance or within a predetermined zone.

The invention thus broadly stated may be embodied in a variety of forms, all of which, however, are based upon the utilization of sound waves or vibrations, transmitted wholly or primarily through the water in which the mine is placed, These waves or vibrations are taken up by, or set up vibrations in, amicro-telephonic transmitter, which, through suitable intermediate devices gradually closes an electric circuit which in turn directly or intermediately ignites the detonating charge.

This gradual action in closing or completing the igniting or detonating circuit is ofprime importance, in that it permits the apparatus to begin its operation while the vessel is at a relatively. great distance from the mine, but to complete its work only after a period sufficient to bring the vessel close enough to ensure its destruction or serious injury. It also precludes detonation of the charge by explosion of shells or bombs in its vicinity, since the action of these is momentary only, and entirely too brief to effect a completion or closure of the firing or detonating circuit.

In the accompanying drawings:

Figure 1 is a sectional view of the soundresponsive element and connections;

Figure 2 is a view of the sound-receiver and relay;

Figure 3 is a view of the thermostatic circuit closer, and firing or discharging means, which, with the parts shown in Figs. 1 and 2 complete the apparatus;

Fi ure 4 is a face view of the thermostatic circuit closer;

Figure 5 is a vertical transverse section through the same.

The apparatus is to be placed in the upper part of a mine A, and may be provided with one or with several micro-telephonic transmitters, as found expedient.

Referring first to Fig. 1, the numeral 1 indicates the diaphragm of a micro-telephonic transmitter 2 of any usual or approved type and ofsuitable dimensions; 2 the carbon-container, chamber, or casing of the microphone; 3 a wire or conductor connecting one of the electrodes of the microphone with one end of the primary winding 4 of an induction coil 5; 6 a wire or conductor connecting the other end of said primary winding with the diaphragm 1, and through it connecting with the other electrode of the microphone, a battery 7 or other source of electric current being included in the circuit so formed. The space between the electrodes of the microphone is filled with carbon granules of usual character, which, being alternately subjected to and relieved of pressure by the inward and outward movements of the diaphragm 1 when the latter is set into vibration by sound waves, causes a pulsating or undulating current to flow through the circuit, as is well understood. The secondary'winding 8 of the induction coil 5 is'connected in circuit with an electromagnet 9, here shown as of two-spool form, the poles of which face and are in proximity to the center of a diaphragm 10, held at its circumference in a suitable supporting shell or casing. At itscenter the diaphragm 10 carries a post or stem 11, the extremity of which forms a contact to co-act with a contact 12 carried by a lever 13 fulcrumed at 14. A spring 15 with suitable tensioning spindle 16 and thumb-wheel or button 17 serves normally to hold together the contacts 11 and 12.

An electric circuit, comprising a battery 18 or other source of electric current, an ele'ctromagnet 19, wire or conductor 20, the diaphragm 10, post 11, contact 12, lever 13, and insulated supporting post 21, serves through the energization of the electromagnet 19 to attract and hold against a stop 22, a lever 23,- having an armature 24 facing the ole of magnet 19, and carrying a contact block 25. A light spring 26, insuflicient to overcome'the attractive power of the magnet 19, tends to draw the lever 23 and its armature 24 away from the electromagnet, and to carry the contact 25 to and hold it f'couples, Such a body, whether in spiral or other form, tends by the more ra id expansion of one than of the other of t 1e two elements, to change its shape, warping or bending in one or the other direction according to the rise or fall of temperature, and consequent more rapid expansion or contraction of the substance having the higher co-eflicient of expansion. In the illustration here given, the coil is arranged to uncoil under rise of temperature, and to re-coil under fall thereof, or in other words, to move the circuit closing hand clockwise on rise of temperature. One end of the coil is' adjustably attached to a support 29, while the other extremity is secured to the rotatable spindle of circuit closing hand 31 of suitable conducting'metal, havlng a contact block 32, which upon movement of circuit closing hand 31 a predetermined distance, is caused to bear against a contact 33 carried by an adjustable companion hand 33 The lever 23 and its contact 25, Fig. 2, constitute part of an electric circuit comprising the supporting block or bracket 34:

and wire or conductor 35, the circuit closing hand 31, spindle '30, the insulated resistance coil 28 wound around the spiral coil 28, wire or conductor 36, resistance 37, battery 38 or other source of electric energy, conductor 39, and contact 27. This circuit will remain open or interrupted so long as the diaphragm 10 is at rest, and lever 23 is held by attraction of magnet 19 against'the stop 22, or so long in other words, as contacts 25 and 27 are separated. The resistance 37 is in the nature of a rheostat, or is arranged to be made variable in any usual and well-known way.

Contact hand 33 is connected with one pole of battery 38 or other source of electric energy, by a conductor 40 in a shunt around the resistance or rheostat 37, the other pole of battery 38 being connected with contact block 27 by wire or conductor 39, as before stated. Included in the conductor 40 and located Within the detonating or igniting chamber ll of the mine A, is a device for detonating or firing the mine. In the drawing this is represented as a heating coil 42 of fine wire, which may be of platinum, German silver, or other suitable metal or alloy capable of withstanding high temperature and offering resistance suflicient to cause rapid heating. Any equivalent means of firing or discharging the mine may of course be employed, and it is to be understood that the heating coil is merely illustrative of a class, or represents conventionally an igniting or deto-nating device of any well-known type. ing this igniting or detonating device is normally open by reason of separation of the contacts 32 and 33, and will be closed or completed only when said contacts are brought together.

With the apparatus constructed and arranged as above set forth, and properly adjusted, its operation is as follows:

The diaphragm ljbeing exposed at the outside of the mine and immersed with the mine in the water, will take up sound vibra tions occurring within the zone of its receptivity and transmitted through the water. Through the vibrations thus caused, the diaphragm will alternately compress and relieve from pressure the carbon granules contained in the microphonic chamber 2, and will cause a series of undulations or The circuit includpulsations of current from the battery or.

source 7 through the conductor 6, diaphragm 1, microphone 2, conductor 3, and primary winding 4 of induction coil 5. This in turn will set up pulsations or undulations of current in the secondary winding 8 and in the coils of magnets 9 in circuit with said secondary winding, causing the magnets alternately to attract and release or repel diaphragm 10, throwing the same into rapid vibration, and causing post or stem 11 to force backward the contact 12 and its carrying lever 13. The great rapidity of these movements and the inertia of the lever 13, will cause the contacts '11 and 12 to be separated, contact 12 being carried by its momentum beyond the range of move-- ment of contact 11. This separation, occurring with a frequency proportionate to the rate of vibration ofdiaphragm 10, causes the current of battery 18 to flow in a rapid succession of pulsations through the windings of electrcmagnet 19 and its circuit before described. For the periods of separation of the contacts 11 and 12, the magnet 19 is tie-energized,- and the lever 23 is drawn by spring 26 away from magnet 19, causing contacts 25 and 27 to meet, thus completing the circuit of battery 38 through conductor 39, contacts 27- and 25, lever 23, bracket 34:,conductor 35, resistance coil 28., conductor 36 and resistance 37 back to bat-, tery. In practice, the parts may be sopro portioned or adjusted as to hold contacts 25 and 27 together during vibration of diaphragm 1. I

The current flowing through resistance coil 28 generates heat therein, causing the thermostatic coil 28 to expand, and gradually to swing the circuit closing hand .31 with its contact block 32 toward contact 33 of the. hand 33. When the heat builds up sufliciently to carry contact 32 into'bearing with contact 33, a circuit is established from battery 38 by conductor 39, contacts 27 and 25, lever 23, conductor 35, spindle 30, circuit closing hand 31, contacts 32 and 33, hand 33, and wire or conductor back to battery 38, the current flowing in its passage through the described circuit, through the device 42, which as above explained, serves to ignite the detonating charge of the mine A. When electrical connect-ion is established between contacts 32 and 33, the current will flow mainly through the circuit just described because of the resistances included in the connection between the circuit wire or conductor 35 and battery 38, hence will be adequate to cause prompt heating of the igniting coil 42, or functioningpf any other form of detonator.

Various adjustments of the apparatus will be necessary to its intended operation. These will of course be variable according to conditions obtaining in any given case, but the. usual provisions are made throughout for such adjustments, and are conventionally indicated.

As pointed out in the opening of this specification, it is of importance that the apparatus act gradually to close the firing or detonating circuit The mine constitutes the central point of a zone of predetermined radius which is to be protected. The radius of receptivity of diaphragm. 1, that is to say the radius within which it will be affected by sound vibrations set up in the water by an approaching vessel or by other continuing sound-producing body or agent, may be assumed for purposes of illustration merely, to be 200 feet; and the radius of destructivity of the mine, that is the radius within which explosion of the mine would destroy or seriously injure an approaching or passing vessel, may be assumed to be 100 feet. Adjustments of the mechanism will hence be made which will cause the diaphragm 1 to begin its vibration when the vessel or other object approaches within a radius of 200 feet, and this in turn will cause a pulsatory current to flow through the windings of magnet 9 in circuit with the secondary winding 8 of the induction coil 5, the primary winding 4 of which is in circ'uit with battery or source 7. The vibration of diaphragm 10 will cause the momentary de-energization of magnet 19, which will hence release lever'23, causing the. circuit of battery 38 to be closed by meeting of contacts 25 and 27, and bringing resistance coil 28' wound around the thermostatic coil 28, into circuit with said battery 38,

According to the radius of receptivity, the 1 contact hand 33 will be set or adjusted to require a length of time for the requisite heating of the thermostatic device 28 to carry contact 32 into bearing with contact 33, equal to the estimated time required for the travel of the vessel or other body from the outer limit of the zone of receptivity of diaphragm 1 into the zone of destructivity of the mine; in other words, under the assumed radii, to a point within 100 feet of the mine. By the time the vessel reaches the zone of destructivity, the contact being established between contact points 32 and 33, the detonating circuit before traced out and including battery or source 38 and heater or discharging device 42, will be completed, and the mine exploded.

In Figs. 4 and 5 I have shown a common form of setting device for the contact hand 33', which hand is frictionally held wher ever set. Said adjusting device comprises a cyllndrical stem 43 having a milled head and co-axial with spindle 30, said stem being seated in a tubular guide in the thermostat casing, and pressed outward by an encircling spring 44. The inner end of stem 43 carries a radial arm 45, the end 46 of which is bent at a right angle or into a planeparallel with that of the axis of the stem. By turning the stem 44 to carry the projecting end 46 to one or the other side of contact hand 33', pressing said stem inward to carry said end 46 past hand 33', and then turning the same in the reverse direction, said hand can be adjusted forward or backward as desired. No claim is .made to this device,

however.

In the event that a vessel or other body enter and leave the zone of receptivity withoutentering the zone of destructivity, the

diaphragm 1 will cease to vibrate, the flow of current through the thermostat will cease, the coil will-c001,.and the circuit closing hand will move back to its initial position, thus restoring all parts to their normal adjustments. The mechanism will hence' be speedily reset or properly adjusted to perform its cycle of operations in the time originally predetermined.

The proportions of the different elements of the apparatus must of course depend up- 1 on many conditions which are more or less. variable in actual use, and hence I do not restrict myself to any specific dimensions or proportions. y

In the chosen illustration I have represented electrical devices for effecting the connection between the sound-responsive diaphragm 1 and the discharging "means 42, and such I deem preferable to strictly mechanical connections or devices, because of the facility with which they can be installed,

their promptness of action, and general efiiciency. It is tobe understood, however, that I do not restrict myself in this re ard. Mechanical connections and devices, initialsound-responsive element, may be employed,

- the only essential requirement being that the discharging device or means be caused to act only after the sound-responsive device has operated a predetermined minimum length of time.

The term mine is used in a comprehen'sive sense, and is meant to include all that class of explosive'devices employed for tlie'protection of harbors, channels, and similar places, and designed to be anchored, moored or fixed in position and exploded through contact or in other wellknown ways. The improvements here described may be used in addition to other discharging means, or in lieu thereof, as deemed expedient in any given case or situation:

The bimetallic thermostat is here represented because deemed efiicient and peculiar- 1y suitable to conditions of use, but typifies thermostats of variant form or construction. Thermostats and thermostatic circuit closers, bimetallic, mercurial, and mechanical, with provision for determining the range of movement of the circuit closing hand for given variations of temperature, are well known in certain other arts, and selection of any suitable type in carrying out this invention may of course be made. So, too, any-gradually-acting, retarded, or governed circuit closer may be employed to complete the "discharging connection, provided it be arranged to act under the control of the initial sound-responsive device. Other types of circuit interrupter may be substituted for the cont-acts 11 and 12 and their co-acting parts.

or overlap one another, to guard against passage of a vessel through or across the arrier thus provided.

If two or more sound-responsive devices are employed, as may be done, each may be wired to or electrically connected with the primary winding of one and the same induction coi1, so that from that point no further and connections between the sound-responsive device and the discharging means, includin a relay for building up energy initiated y the sound-responsive device, and a connection-completing device capable ofbeing set-to re uire a predetermined interval of time to e eet completion of the connection with the discharging means.

2. In combination with and as elements of an explosive mine,.a microphonic receiver; an electric circuit; a discharging device included in said circuit and arranged to function on closing of saidcircuit; and a circuit closer for said circuit, operable through vibration of the sound-responsive device, and serving to close the circuit upon the lapse of a predetermined period of time beginning with the reception of sound waves by the sound-responsive device.

In testimony whereof I have signed my name to-this specification.

JOHN'JIDUFFIE. 

